while they are sliding. In the face-centered structure such planes may be found in many directions in the crystal, so that there is very little tendency for the crystal to crack-the metal is ductile or tenacious. I t is easily bent without breaking, and may be hammered, drawn into wire, etc. The reverse is generally true of body-centered structures. Here the planes which contain closely packed atoms are not held together very tightly, because every atom in one of the planes is linked to only two atoms in the plane above it and to two in the plane below it. When these planes slide on each other they tend to crack apart. Therefore, such metals cannot be worked mechanically as easily as the &her type. Such are some of the facts which have been learned with one of the three methods of X-ray chemical analysis-spectrum analysis, absorption band analysis and diffraction pattern analysis.
Small Doses of Poison Pep Up Soil Bacteria. Small amounts of chemical substances in the soil, many of them poisonous to bacteria, seem t o have a stimulating effect on these microscopic organisms as well as on the bigger plants whose lives they affect, according to Dr. J. E. Greaves of the Utah Agricultural Experiment Station. Discussing his studies an the rise and decline of sail bacteria populations before the First International Congress of Soil Sciences in Washington, Dr. Greaves stated that he has found this stimulating effect followed the use of arsenic, of sodium sulfate, and of sodium chloride, all of which are poisonous to bacteria in stronger concentrations. The explanation which Dr. Greaves offen for this phenomenon is that the effect of the poisons is not a direct one. He inclines t o the opinion that there is in the soil, along with the bacteria, a destructive substance or principle allied to the bacteriophage, prominent in recent medical research, and that the poisons cause increases or decreases in its activity, thereby causing the fluctuations in the numbers or bacteria.-3cience Seruice Lord Kelvin Honored a s Scientific Pioneer. Science celebrated, June 26th, the 103rd anniversary of the birth of Lord Kelvin. He was one of the most famous scientific men the world has known. His laboratory, an old wine cellar a t Glasgow University, set the pace for scientific research. He made the sea safe by perfecting the mariner's magnetic compass, inventing the sounding machine, blinking lighthouses, and the tide-predicting machine. He engineered the first deep-sea cable across the Atlantic and invented the mirror galvanometer that detected the feeble electric impulses. He laid the foundations of thermodynamics on which refrigeration and heating applications rest. IIe discovered lundamentd electrical principles. I l e Rave his support to Bell and his tclcphone 2nd helped estnhlish it. - He aided Marcmi and the first wireless company. He took out seventy patents. He died only twenty years ago and lived t o see his inventions and discoveries create revolutions and change our mode of life.--Science Service
